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 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.io;


/**
 * Piped character-input streams.
 *
 * @author Mark Reinhold
 * @since JDK1.1
 */

public class PipedReader extends Reader {

  boolean closedByWriter = false;
  boolean closedByReader = false;
  boolean connected = false;

  /* REMIND: identification of the read and write sides needs to be
     more sophisticated.  Either using thread groups (but what about
     pipes within a thread?) or using finalization (but it may be a
     long time until the next GC). */
  Thread readSide;
  Thread writeSide;

  /**
   * The size of the pipe's circular input buffer.
   */
  private static final int DEFAULT_PIPE_SIZE = 1024;

  /**
   * The circular buffer into which incoming data is placed.
   */
  char buffer[];

  /**
   * The index of the position in the circular buffer at which the
   * next character of data will be stored when received from the connected
   * piped writer. <code>in&lt;0</code> implies the buffer is empty,
   * <code>in==out</code> implies the buffer is full
   */
  int in = -1;

  /**
   * The index of the position in the circular buffer at which the next
   * character of data will be read by this piped reader.
   */
  int out = 0;

  /**
   * Creates a <code>PipedReader</code> so
   * that it is connected to the piped writer
   * <code>src</code>. Data written to <code>src</code>
   * will then be available as input from this stream.
   *
   * @param src the stream to connect to.
   * @throws IOException if an I/O error occurs.
   */
  public PipedReader(PipedWriter src) throws IOException {
    this(src, DEFAULT_PIPE_SIZE);
  }

  /**
   * Creates a <code>PipedReader</code> so that it is connected
   * to the piped writer <code>src</code> and uses the specified
   * pipe size for the pipe's buffer. Data written to <code>src</code>
   * will then be  available as input from this stream.
   *
   * @param src the stream to connect to.
   * @param pipeSize the size of the pipe's buffer.
   * @throws IOException if an I/O error occurs.
   * @throws IllegalArgumentException if {@code pipeSize <= 0}.
   * @since 1.6
   */
  public PipedReader(PipedWriter src, int pipeSize) throws IOException {
    initPipe(pipeSize);
    connect(src);
  }


  /**
   * Creates a <code>PipedReader</code> so
   * that it is not yet {@linkplain #connect(java.io.PipedWriter)
   * connected}. It must be {@linkplain java.io.PipedWriter#connect(
   *java.io.PipedReader) connected} to a <code>PipedWriter</code>
   * before being used.
   */
  public PipedReader() {
    initPipe(DEFAULT_PIPE_SIZE);
  }

  /**
   * Creates a <code>PipedReader</code> so that it is not yet
   * {@link #connect(java.io.PipedWriter) connected} and uses
   * the specified pipe size for the pipe's buffer.
   * It must be  {@linkplain java.io.PipedWriter#connect(
   *java.io.PipedReader) connected} to a <code>PipedWriter</code>
   * before being used.
   *
   * @param pipeSize the size of the pipe's buffer.
   * @throws IllegalArgumentException if {@code pipeSize <= 0}.
   * @since 1.6
   */
  public PipedReader(int pipeSize) {
    initPipe(pipeSize);
  }

  private void initPipe(int pipeSize) {
    if (pipeSize <= 0) {
      throw new IllegalArgumentException("Pipe size <= 0");
    }
    buffer = new char[pipeSize];
  }

  /**
   * Causes this piped reader to be connected
   * to the piped  writer <code>src</code>.
   * If this object is already connected to some
   * other piped writer, an <code>IOException</code>
   * is thrown.
   * <p>
   * If <code>src</code> is an
   * unconnected piped writer and <code>snk</code>
   * is an unconnected piped reader, they
   * may be connected by either the call:
   *
   * <pre><code>snk.connect(src)</code> </pre>
   * <p>
   * or the call:
   *
   * <pre><code>src.connect(snk)</code> </pre>
   * <p>
   * The two calls have the same effect.
   *
   * @param src The piped writer to connect to.
   * @throws IOException if an I/O error occurs.
   */
  public void connect(PipedWriter src) throws IOException {
    src.connect(this);
  }

  /**
   * Receives a char of data. This method will block if no input is
   * available.
   */
  synchronized void receive(int c) throws IOException {
    if (!connected) {
      throw new IOException("Pipe not connected");
    } else if (closedByWriter || closedByReader) {
      throw new IOException("Pipe closed");
    } else if (readSide != null && !readSide.isAlive()) {
      throw new IOException("Read end dead");
    }

    writeSide = Thread.currentThread();
    while (in == out) {
      if ((readSide != null) && !readSide.isAlive()) {
        throw new IOException("Pipe broken");
      }
            /* full: kick any waiting readers */
      notifyAll();
      try {
        wait(1000);
      } catch (InterruptedException ex) {
        throw new java.io.InterruptedIOException();
      }
    }
    if (in < 0) {
      in = 0;
      out = 0;
    }
    buffer[in++] = (char) c;
    if (in >= buffer.length) {
      in = 0;
    }
  }

  /**
   * Receives data into an array of characters.  This method will
   * block until some input is available.
   */
  synchronized void receive(char c[], int off, int len) throws IOException {
    while (--len >= 0) {
      receive(c[off++]);
    }
  }

  /**
   * Notifies all waiting threads that the last character of data has been
   * received.
   */
  synchronized void receivedLast() {
    closedByWriter = true;
    notifyAll();
  }

  /**
   * Reads the next character of data from this piped stream.
   * If no character is available because the end of the stream
   * has been reached, the value <code>-1</code> is returned.
   * This method blocks until input data is available, the end of
   * the stream is detected, or an exception is thrown.
   *
   * @return the next character of data, or <code>-1</code> if the end of the stream is reached.
   * @throws IOException if the pipe is <a href=PipedInputStream.html#BROKEN>
   * <code>broken</code></a>, {@link #connect(java.io.PipedWriter) unconnected}, closed, or an I/O
   * error occurs.
   */
  public synchronized int read() throws IOException {
    if (!connected) {
      throw new IOException("Pipe not connected");
    } else if (closedByReader) {
      throw new IOException("Pipe closed");
    } else if (writeSide != null && !writeSide.isAlive()
        && !closedByWriter && (in < 0)) {
      throw new IOException("Write end dead");
    }

    readSide = Thread.currentThread();
    int trials = 2;
    while (in < 0) {
      if (closedByWriter) {
                /* closed by writer, return EOF */
        return -1;
      }
      if ((writeSide != null) && (!writeSide.isAlive()) && (--trials < 0)) {
        throw new IOException("Pipe broken");
      }
            /* might be a writer waiting */
      notifyAll();
      try {
        wait(1000);
      } catch (InterruptedException ex) {
        throw new java.io.InterruptedIOException();
      }
    }
    int ret = buffer[out++];
    if (out >= buffer.length) {
      out = 0;
    }
    if (in == out) {
            /* now empty */
      in = -1;
    }
    return ret;
  }

  /**
   * Reads up to <code>len</code> characters of data from this piped
   * stream into an array of characters. Less than <code>len</code> characters
   * will be read if the end of the data stream is reached or if
   * <code>len</code> exceeds the pipe's buffer size. This method
   * blocks until at least one character of input is available.
   *
   * @param cbuf the buffer into which the data is read.
   * @param off the start offset of the data.
   * @param len the maximum number of characters read.
   * @return the total number of characters read into the buffer, or <code>-1</code> if there is no
   * more data because the end of the stream has been reached.
   * @throws IOException if the pipe is <a href=PipedInputStream.html#BROKEN>
   * <code>broken</code></a>, {@link #connect(java.io.PipedWriter) unconnected}, closed, or an I/O
   * error occurs.
   */
  public synchronized int read(char cbuf[], int off, int len) throws IOException {
    if (!connected) {
      throw new IOException("Pipe not connected");
    } else if (closedByReader) {
      throw new IOException("Pipe closed");
    } else if (writeSide != null && !writeSide.isAlive()
        && !closedByWriter && (in < 0)) {
      throw new IOException("Write end dead");
    }

    if ((off < 0) || (off > cbuf.length) || (len < 0) ||
        ((off + len) > cbuf.length) || ((off + len) < 0)) {
      throw new IndexOutOfBoundsException();
    } else if (len == 0) {
      return 0;
    }

        /* possibly wait on the first character */
    int c = read();
    if (c < 0) {
      return -1;
    }
    cbuf[off] = (char) c;
    int rlen = 1;
    while ((in >= 0) && (--len > 0)) {
      cbuf[off + rlen] = buffer[out++];
      rlen++;
      if (out >= buffer.length) {
        out = 0;
      }
      if (in == out) {
                /* now empty */
        in = -1;
      }
    }
    return rlen;
  }

  /**
   * Tell whether this stream is ready to be read.  A piped character
   * stream is ready if the circular buffer is not empty.
   *
   * @throws IOException if the pipe is <a href=PipedInputStream.html#BROKEN>
   * <code>broken</code></a>, {@link #connect(java.io.PipedWriter) unconnected}, or closed.
   */
  public synchronized boolean ready() throws IOException {
    if (!connected) {
      throw new IOException("Pipe not connected");
    } else if (closedByReader) {
      throw new IOException("Pipe closed");
    } else if (writeSide != null && !writeSide.isAlive()
        && !closedByWriter && (in < 0)) {
      throw new IOException("Write end dead");
    }
    if (in < 0) {
      return false;
    } else {
      return true;
    }
  }

  /**
   * Closes this piped stream and releases any system resources
   * associated with the stream.
   *
   * @throws IOException if an I/O error occurs.
   */
  public void close() throws IOException {
    in = -1;
    closedByReader = true;
  }
}
